1. Field of the Invention
The invention is directed in general to a shaft seal which includes a sealing lip provided on an elastomeric portion of a first annular member which is in rotating sealing contact with a sealing face of a second annular member. The invention is particularly directed to an annular elastomeric support portion provided on the first annular member for supporting axial loads on a radial surface of the second annular member via protrusions integrally formed on the support portion.
2. Description of Prior Developments
Unitized shaft seals are well known in the art, as disclosed in U.S. Pat. No. 3,685,841 and German Patent DE-OS 1,942,659. Such seals are sometimes called "cassette" seals or "unitized" seals because they include a counter-race necessary for sealing engagement with a sealing lip provided on a separate support or case and can readily be assembled and installed as an integral structural element.
A problem arises during installation of a unitized seal insofar as considerable axial installation loads are applied to the annular seal members as the seal is press-fit into a bore formed in a first structural member. These loads are applied to the second annular member via the first rigid annular member and its elastomeric support portion when the second annular member is fitted onto a second member, such as a shaft, which is rotatable relative to the first member. In practical use, the axial loads may, for instance, be in the range of 3t to 5t.
In their installed state, the two relatively rotatable parts of the unitized cassette seal remain axially fixed and abutted against one another. In use, as the second annular member rotates in operation relative to the first annular member under the influence of the axial installation load, high friction and considerable wear are caused as long as the axial abutment and loading between the two seal members exists. This can possibly result in premature failure of the shaft seal.